Cellular networks such as the Global System for Mobile Communications (GSM) and Wideband Code Division Multiple Access (WCDMA) provide wide-area wireless coverage for voice and data services. Wireless local area network (WLAN) systems provide wireless coverage over small local areas, typically with higher bandwidth than cellular networks.
FIG. 1 is an illustrative drawing of the coverage areas of two base stations, BS1 and BS2, in an existing cellular communication system. The coverage areas of two WLANs, WLAN1 and WLAN2, are shown providing services within small regions inside the coverage areas of the cellular base stations. Mobile terminals such as a laptop computer with a PCMCIA card have the capability of using either a cellular network or a WLAN to satisfy the voice and data needs of the user. The user may find it desirable, for example, to use a WLAN connection whenever higher bandwidth capabilities are required, while using the cellular network for voice and other delay-critical services. To use a WLAN, however, the user must first find a suitable WLAN.
When a mobile terminal is connected to a cellular network, it is very power-inefficient for it to constantly search for WLAN systems. If scanning for a LAN system is performed too often, the battery life of the mobile terminal is adversely affected. If scanning is not performed often enough, an opportunity to connect to a WLAN system may be missed. There are no known solutions to the problem of determining when a mobile terminal should scan for a WLAN.